Former Giants running back Brandon Jacobs, shown in an exhibition game against Minnesota, got his only regular-season carry with the 49ers in New Orleans on Sunday.

Former Giants running back Brandon Jacobs, shown in an exhibition game against Minnesota, got his only regular-season carry with the 49ers in New Orleans on Sunday.

Photo: Lance Iversen, The Chronicle

49ers place Kendall Hunter on IR

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Running back Kendall Hunter landed on season-ending injured reserve Tuesday, giving the 49ers another offensive question beyond their high-profile quarterback debate - namely, who will complement Frank Gore for the last five games and into the playoffs?

The 49ers could stick with a speedy, Hunter-like back and finally unveil rookie La- Michael James. They also could go big and give carries to once-invisible Brandon Jacobs, or they could fall somewhere in between and expand the role of Anthony Dixon.

This much is certain: Hunter spelled Gore with panache and productivity, gaining 371 yards on 72 carries (a 5.2 average) and offering a quick, dynamic change of pace. He tore his Achilles tendon in the third quarter of Sunday's victory in New Orleans, on the same play on which wide receiver Kyle Williams tore the ACL in his left knee.

The 49ers placed both Hunter and Williams on IR, officially ending their seasons.

"Two guys who help our team," Gore said. Asked specifically about Hunter, Gore replied, "That's a big loss. I respect his game - everybody on the team respects his game. Kendall can make a big play any time."

Hunter's strong play allowed the 49ers to lighten Gore's load. He has carried the ball 20 or more times in only two of 11 games this season; his average of 16 rushing attempts per game is his lowest since he became a full-time starter in 2006.

Jacobs brings experience (eighth season) and size (6-foot-4, 256 pounds) but not the speed and elusiveness of Hunter. James, the second-round pick from Oregon, seems like a logical candidate to replace Hunter, though James hasn't played in an NFL regular-season game.

"He and Kendall have similar back speed," Gore said. "He's been working hard and practicing hard. I know he wants to play."

Gore placed his faith in running backs coach Tom Rathman to find a way to fill the void.

"I know Coach Rathman is going to do a great job with whoever he brings up."

Dixon, a special-teams stalwart who also has spent time at fullback, was more animated in his assessment of James. As Pac-12 fans know, he is uncommonly explosive - to the tune of 5,082 yards rushing in three years with the Ducks, including 1,805 last season.

Asked what he expects if James takes most of Hunter's carries, Dixon said, "I expect dynamic plays, man. I watch him every day on the practice field and he's making plays, going up to get the ball. They have him doing Percy Harvin stuff when we're playing teams like that, and he really is a great talent.

"I know he's hungry. He hasn't got the chance to really get his feet wet yet. ... I expect a lot of great plays out of him."

The 49ers tried to fortify their depth at running back by adding undrafted rookie Jewel Hampton to the active roster, from the non-football injury list. Hampton, who had offseason surgery to remove bone spurs in his left foot and missed training camp, returned to practice Nov. 6.

Hampton began his college career at Iowa and missed the 2009 season with an ACL tear in his right knee. He tore the ACL in his left knee in the second game of the 2010 season and transferred to Southern Illinois after the season. He rushed for 1,121 yards and 17 touchdowns at Southern Illinois last year.

This jumble in the backfield follows Monday's news about Williams going down for the season. He was at 49ers headquarters Tuesday, on crutches and with his knee heavily wrapped.

Williams had 14 catches for 212 yards this season and was effective as a slot receiver. The 49ers also have options there, from expanding the role of Randy Moss to giving unused No. 1 draft choice A.J. Jenkins some playing time.

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